Methods for sizing project and feeding buffers for critical chain project management are investigated. Experiments indicate that - in the absence of bias, and for certain classes of bias - buffer consumption is independent of the mean duration of a chain. Generally the popular method - a buffer size equal to 50% of the longest path leading to it - gives rise to excessively large buffers. Buffers sized according to the square root of the sum of squares perform well in the absence of bias, but with bias present the performance is unacceptably poor. A new approach to buffer sizing is proposed.